Numerous configurations have been proposed for building wheeled vehicles over a pair of equally-spaced rails, ranging from intercontinental railroads, narrow-gauged cog railways, computer-assisted robotic inventory retrieval systems, moving beds of machine tools, etc. All such wheel and rail systems require that the wheels be retained upon the rails, either forcibly through the use of flanges, or by virtue of the fact that the weight of the vehicle retains the wheels in a track (such as a V-shaped wheel rolling within a recessed V-shaped channel track). Generally speaking, at least one pair of wheels per vehicle is driven by a solid axle therebetween. However, because the wheels are preferably fixed to the axle and are therefore forced to turn at the same peripheral rotational velocity, many such systems force the wheel positioned radially inwardly during a turn to slip or slide on the rail, since it travels a shorter distance through a turn than the radially outermost wheel. Conventional railroad wheel and rail assemblies solve this problem, as illustrated in FIG. 1, by providing a railroad wheel 10 with an inwardly sloping planar bearing surface 12 which contacts the rail 14. As centrifugal force and the tendency of the wheel assembly to follow a tangent to the curve pushes the vehicle (and the pair of wheels) to one side, in the direction of arrow 16, during a turn in the direction opposite that of arrow 16, the new rolling radius of outer wheel 18 is increased over that of the previous rolling radius. Coincidentally, the innermost wheel 24 also moves in the direction of arrow 16, resulting in a new, shorter rolling radius when compared with the previous rolling radius. Therefore, the innermost wheel 24 travels a shorter distance on the innermost rail 30 than does the outermost wheel 18 on outermost rail 32.
In order to change any rail-mounted vehicle from one set of rails to another, most prior art systems have relied upon means external of the vehicle to effect the change. For instance, in the conventional railroad wheel/rail apparatus illustrated in FIG. 1, the flanges 34 positioned on the inner side of each wheel are utilized to guide the vehicle onto an alternate track, the rails of which are positioned adjacent to the rails 30, 32. Upon engaging the alternate, or turnout rails, the flange forces the wheel to divert its direction in the direction of the turnout rails. During such a change in tracks, the flanges of both wheels must cross one of the rails and a slot must be provided in this rail to permit the wheel flange to traverse the width of the rail.
Although utilizing a different rail and wheel geometry than conventionally utilized, U.S. Pat. No. 2,046,448, De Buigne, provides a flanged wheel, and in some embodiments a notched rail, in order to effect track changes. U.S. Pat. No. 3,788,233, discloses a guided vehicle transportation system having switched wheels effecting changes in vehicle direction.
Therefore, there is a need for a method of transportation, not disclosed in the prior art, whereby lightweight materials may be utilized in a rail transmit system which does not rely on conventional flanged-wheel technology.